Fix deprecation warning in test_MimeWriter.

Lib/test/test_MimeWriter.py

@@ -8,12 +8,9 @@ This should generate Barry's example, modulo some quotes and newlines.
 """
 
 import unittest, StringIO
-from test.test_support import run_unittest
-
-import warnings
-warnings.filterwarnings("ignore", "the MimeWriter module is deprecated.*",
-                        DeprecationWarning)
+from test.test_support import run_unittest, import_module
 
+import_module("MimeWriter", deprecated=True)
 from MimeWriter import MimeWriter
 
 SELLER = '''\